The effect of N,N,N＇,N＇-tetraalkyl terephthalamide （TATA） on the non-isothermal crystallization and melting characteristics ofpolypropylene （PP） was studied. The addition of TATA can lead to the formation ofβ-c...The effect of N,N,N＇,N＇-tetraalkyl terephthalamide （TATA） on the non-isothermal crystallization and melting characteristics ofpolypropylene （PP） was studied. The addition of TATA can lead to the formation ofβ-crystal PP. With the increase in TATA concentration the degree of crystallinity for β-crystal PP increased significantly, and that for a-crystal PP decreased, which indicated that TATA effectively induced the formation of β-crystal PP. WAXD also revealed the existence of β-crystal PP after the introduction of TATA into PP. PP containing TATA crystallized at a temperature range of 5-10℃ higher than that of pure PP, and the half-crystallization time （t1/2） and Avrami exponent （n） of PP at the same cooling rate were decreased by the addition of TATA, indicating that TATA influenced the crystallization rate and crystallization growth mode of PP. The rate constant of crystallization of PP containing TATA （Zc） was larger than that of pure PP, which further indicated that the crystallization of PP was accelerated by the addition of TATA.展开更多
In our current work, the effect of the shear temperature on the growth of β-crystal in isotactic polypropylene（iPP） with β-nucleating agent is investigated by means of in situ two-dimensional wide-angle X-ray diff...In our current work, the effect of the shear temperature on the growth of β-crystal in isotactic polypropylene（iPP） with β-nucleating agent is investigated by means of in situ two-dimensional wide-angle X-ray diffraction（2 D-WAXD）. At low shear temperatures, the formed shear-induced oriented precursors are hard to relax back to random coiled state due to the weak mobility of molecular chains. Therefore, plenty of oriented α-crystals are induced by shear-induced oriented precursors, while β-crystal is greatly depressed. As the shear temperature increases, oriented β-crystal gradually increases along with the decrease of α-crystal. It is deduced that the shear temperature at which the content of β-crystal increases to the（maximum） value found in quiescent crystallization is almost the same as that at which the accelerating effect of flow on crystallization kinetics is completely erased. Our work manifests its significance in regulating β-crystal and thus in the structure and property manipulation of i PP.展开更多
The nature of the crystalline phase of poly(vinylidene fluoride)(PVDF) in compatible blends with poly(ethyl methacrylate)(PEMA) was investigated by using X-ray diffraction(XRD), infrared microscopy(IR) and differentia...The nature of the crystalline phase of poly(vinylidene fluoride)(PVDF) in compatible blends with poly(ethyl methacrylate)(PEMA) was investigated by using X-ray diffraction(XRD), infrared microscopy(IR) and differential scanning calorimetry(DSC). The βphase of PVDF was observed after quenching from the melt and further annealing above the glass transition temperature over a composition range. The PVDF/PEMA blend with weight ratio of 3:2 has formed higher content of PVDF β crystals than others. By taking advantage of fast cooling rate of ultrafast differential scanning calorimeter(UFDSC), the quenching process of blends was modeled and tested simultaneously, and the melting behavior of β crystals in all blends was investigated. Three types of crystallization behavior of βphase PVDF in blends were found after quenching-annealing at different temperatures.展开更多
The compatibility between isotactic polypropylene（iPP） and ethylene-propylene-diene terpolymer（EPDM） in the blends was studied. SAXS analysis indicates that iPP and EPDM phases in the binary blend are incompatible...The compatibility between isotactic polypropylene（iPP） and ethylene-propylene-diene terpolymer（EPDM） in the blends was studied. SAXS analysis indicates that iPP and EPDM phases in the binary blend are incompatible. Isothermal crystallization behaviors of iPP in phase-separated iPP/EPDM were studied by in situ POM equipped with a Linkam shear hot stage. It was found that typical spherulites of iPP were formed both in neat iPP and in iPP/EPDM blends. The radial growth rate（d R/dt） of spherulites of iPP in the blend was not influenced by EPDM phases. Further investigations on isothermal crystallization of iPP in iPP/EPDM after shear with a fixed shear time showed that the crystallization rate of iPP in the blends increased with increasing shear rates, whereas, the crystallization rate was much lower than that of neat iPP. WAXD results showed that β-crystal iPP was formed in neat iPP as well as in iPP/EPDM blends after shearing and the percentage of β-crystal bore a relationship to the applied shear rate. The presence of EPDM resulted in lower percentage of β-crystal in the blends than that in neat iPP under the same constant shear conditions. SAXS experiments revealed that shear flow could induce formation of oriented lamellae in iPP and iPP in the blends, and the presence of EPDM led to a reduced fraction of oriented lamellae.展开更多
基金This work was supported by the Scientific Research Foundation for Returned Overseas Chinese Scholars, Ministry of Education.
文摘The effect of N,N,N＇,N＇-tetraalkyl terephthalamide （TATA） on the non-isothermal crystallization and melting characteristics ofpolypropylene （PP） was studied. The addition of TATA can lead to the formation ofβ-crystal PP. With the increase in TATA concentration the degree of crystallinity for β-crystal PP increased significantly, and that for a-crystal PP decreased, which indicated that TATA effectively induced the formation of β-crystal PP. WAXD also revealed the existence of β-crystal PP after the introduction of TATA into PP. PP containing TATA crystallized at a temperature range of 5-10℃ higher than that of pure PP, and the half-crystallization time （t1/2） and Avrami exponent （n） of PP at the same cooling rate were decreased by the addition of TATA, indicating that TATA influenced the crystallization rate and crystallization growth mode of PP. The rate constant of crystallization of PP containing TATA （Zc） was larger than that of pure PP, which further indicated that the crystallization of PP was accelerated by the addition of TATA.
基金supported by the National Key R&D Program of China(2019YFA0706802)Shenzhen Science and Technology Program(CJGJZD20210408092602006)the Science and Technology Major Project of Henan Province(221100240400)。
基金financially supported by the National Natural Science Foundation of China(Nos.51473135,51503170 and 21676217)the Opening State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme 2015-4-22)the Fundamental Research Funds for the Central Universities(No.3102016BJY01)
文摘In our current work, the effect of the shear temperature on the growth of β-crystal in isotactic polypropylene（iPP） with β-nucleating agent is investigated by means of in situ two-dimensional wide-angle X-ray diffraction（2 D-WAXD）. At low shear temperatures, the formed shear-induced oriented precursors are hard to relax back to random coiled state due to the weak mobility of molecular chains. Therefore, plenty of oriented α-crystals are induced by shear-induced oriented precursors, while β-crystal is greatly depressed. As the shear temperature increases, oriented β-crystal gradually increases along with the decrease of α-crystal. It is deduced that the shear temperature at which the content of β-crystal increases to the（maximum） value found in quiescent crystallization is almost the same as that at which the accelerating effect of flow on crystallization kinetics is completely erased. Our work manifests its significance in regulating β-crystal and thus in the structure and property manipulation of i PP.
基金financially supported by the National Natural Science Foundation of China (Nos. 21474049, 51673094 and 21404055)Tianshan Scholars Program by Yili Normal Universitythe Shenzhen Science and Technology Innovation Committee (Nos. JCYJ20160608140827794, JCYJ20160531151102203 and JCYJ20170818110206085)
文摘The nature of the crystalline phase of poly(vinylidene fluoride)(PVDF) in compatible blends with poly(ethyl methacrylate)(PEMA) was investigated by using X-ray diffraction(XRD), infrared microscopy(IR) and differential scanning calorimetry(DSC). The βphase of PVDF was observed after quenching from the melt and further annealing above the glass transition temperature over a composition range. The PVDF/PEMA blend with weight ratio of 3:2 has formed higher content of PVDF β crystals than others. By taking advantage of fast cooling rate of ultrafast differential scanning calorimeter(UFDSC), the quenching process of blends was modeled and tested simultaneously, and the melting behavior of β crystals in all blends was investigated. Three types of crystallization behavior of βphase PVDF in blends were found after quenching-annealing at different temperatures.
基金financially supported by the National Natural Science Foundation of China(No.51033004)the Natural Science Foundation of Tianjin(No.12JCYBJC11900)
文摘The compatibility between isotactic polypropylene（iPP） and ethylene-propylene-diene terpolymer（EPDM） in the blends was studied. SAXS analysis indicates that iPP and EPDM phases in the binary blend are incompatible. Isothermal crystallization behaviors of iPP in phase-separated iPP/EPDM were studied by in situ POM equipped with a Linkam shear hot stage. It was found that typical spherulites of iPP were formed both in neat iPP and in iPP/EPDM blends. The radial growth rate（d R/dt） of spherulites of iPP in the blend was not influenced by EPDM phases. Further investigations on isothermal crystallization of iPP in iPP/EPDM after shear with a fixed shear time showed that the crystallization rate of iPP in the blends increased with increasing shear rates, whereas, the crystallization rate was much lower than that of neat iPP. WAXD results showed that β-crystal iPP was formed in neat iPP as well as in iPP/EPDM blends after shearing and the percentage of β-crystal bore a relationship to the applied shear rate. The presence of EPDM resulted in lower percentage of β-crystal in the blends than that in neat iPP under the same constant shear conditions. SAXS experiments revealed that shear flow could induce formation of oriented lamellae in iPP and iPP in the blends, and the presence of EPDM led to a reduced fraction of oriented lamellae.
